In a liquid crystal projector, white source light is separated into beams of its three primary colors. Each beam is then infused with an image by an imaging device, for example a miniature liquid crystal light valve (micro-LCD). Finally, the three beams are recombined into a single image and projected onto a display surface (a screen).
The micro LCD's generate a representation of the image to be projected by using many small picture elements referred to as pixels. Therefore, the above mentioned beams of light that emerge from the micro-LCD's are pixellated representations of the particular color components of the image. Thus, an accurate projected image requires that the pixels of the three infused beams be precisely aligned during the recombination step, meaning that the micro-LCD's themselves must be carefully positioned. In order to optimally orient the micro-LCD's the following requirements must be met.
(1) 6 degree of freedom (dof) adjustment capability must be available. Both rotation and linear translation with respect to three perpendicular axes are required in order to ensure that proper image alignment can be achieved.
(2) Adjustment mechanisms must have high resolution controls. Because of the small size of the pixels, direct manual adjustments are too crude to achieve proper alignment. Some sort of interface must be provided which can transform relatively large-scale operator inputs into micro-LCD motions of a magnitude commensurate with the pixel size.
(3) Adjustment mechanisms must provide positive positioning constraints. Since multiple operations are required to tune all 6 degrees of freedom, intermediate adjustments must have some amount of resistance to motion. Positioning devices typically have some sort of final locking mechanism, but to activate and deactivate that mechanism numerous times over the course of adjustment is cumbersome and often impossible. Therefore, any robust positioning device must provide for physical locating effects, rather than relying on balance, gravity or friction.
(4) The individual magnification of each image must be independently adjustable. There must be a means for making slight adjustments to the projected size of the image from any projection device. This means must be simple, inexpensive, and easy to use such that adjustments can be made quickly during the production process.
In order to achieve the above objectives, it is necessary to have some means for temporarily holding the LCD imager while the described adjustments are made. Such means should be easy to use, should not place any undue stress on the imager such that the image is distorted, and should not in any way harm the imager. It has been known to use a vacuum chuck for this purpose wherein the imager is held to a fixture apparatus by a vacuum. Other known methods have been to physically restrain the imager with a hook, or grabbing apparatus, or the like. In such methods some sort of holding force is required, and this has frequently been provided by a rubber band.
While the above attachment methods and apparatus have performed adequately for the purpose, they have all been somewhat cumbersome in some manner and/or have not held the imager as securely as might be desired. It would be desirable to have some method or means for holding an LCD imager to a fixture apparatus which holds the imager securely, releases quickly and easily, is easy and quick to use, and which does not harm the imager.